Absorption refrigerator of the inert gas type



G. A. GRUBB 2,728,201

ABSORPTION REFRIGERATOR OF THE INERT GAS TYPE Dec. 27, 1955 Filed Oct.20, 1951 2 Sheets-Shea; l

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wzf M Dec. 27, 1955 e. A. GRUBB 2,728,

ABSORPTION REFRIGERATOR OF THE INERT GAS TYPE Filed Oct. 20, 1951 2Sheets-Sheet 2 BY I Qb/I; M

4 ATTORNEY United States Patent a.

ABSORPTION REFRIGERATUR OF THE TNERT GAS TYPE Gunnar Axel Grnbb,Bromzna, Sweden, assignor to Aktiebolaget Elektrolnx, Stockholm, Sweden,a corporation of Sweden Application October 20, 1951, Serial No. 252,312

Claims priority, application Sweden October 25, 1950 Claims. (U. 62-95)My invention relates to absorption refrigeration systems of the inertgas type, and more particularly relates to such a refrigeration systemhaving plural temperature evaporator structure.

It is an object of my invention to provide an improved evaporatorstructure in which several cooling elements operable at differenttemperatures may be effectively employed to cool the thermally insulatedinterior of a refrigerator cabinet and a freezing section disposedtherein. I accomplish this by providing an inert gas circuit having lowand higher temperature evaporators which are formed of piping anddisposed in the interior of a refrigerator, the low temperatureevaporator having a plate-like supporting surface and piping associatedtherewith which is essentially disposed in a single horizontal plane,and the higher temperature evaporator having a relatively extensive heattransfer surface and piping including a horizontally extending portionat a higher level than the horizontal plane of the piping forming thelow temperature evaporator. The higher temperature avaporator is closelyadjacent to the low temperature evaporator and provides an arrangementwhich assures gravity flow of liquid refrigerant successively throughthe higher and low temperature evaporators, respectively, even though anelongated path of flow for liquid refrigerant is provided by the lowtemperature evaporator piping which is disposed essentially in a singlehorizontal plane.

The invention, together with the above and other objects and advantagesthereof, will become apparent as the following description proceeds, andthe features of novelty which characterize my invention will be pointedout with particularity in the claims annexed to and forming a part ofthis specification.

For a better understanding of my invention, reference may be had to thefollowing description taken in connection with the accompanying drawingsin which:

Fig. 1 is a fragmentary front view of the interior of a refrigeratorembodying the invention;

Fig. 2 is a fragmentary side vertical section of the refrigerator shownin Fig. 1 to illustrate details more clearly;

Fig. 3 is a fragmentary perspective view of parts shown in Figs. 1 and2; and

Fig. 4 illustrates more or less diagrammatically the type ofrefrigeration system with which the parts shown in Figs. 1, 2 and 3 areassociated.

Referring to Figs. 1 and 2, a household refrigerator is provided with alow temperature freezing section 11 which is disposed in a highertemperature food storage space 12. The freezing section 11 and storagespace 12 are arranged to be cooled by a plurality of evaporators orcooling elements 14 and 15 which are operable at different temperatures.The evaporators 14 and 15 form part of an absorption refrigerationsystem of the inert gas type and are usually inserted into the storagespace 12 at the rear of the refrigerator in any suitable manner, suchas, for example, through an opening in the rear insulated wall which isadapted to be closed by an insulated closure member 16. A refrigerationsystem of this type is more or less diagrammatically shown in Fig. 4 inwhich the evaporators 14 and 15 are illustrated apart from a householdrefrigerator.

The system illustrated is of a uniform pressure type employing an inertgas or pressure equalizing agent. In Fig. 4 a refrigerant fluid, such asliquid ammonia, for example, is introduced through a conduit 17 into theevaporators 14 and 15.

The refrigerant fluid in evaporators 14 and 15 evaporates and diffusesinto an inert gas, such as hydrogen, for example, to produce arefrigerating effect and abstract heat from the surroundings. Theresulting gas mixture of refrigerant and inert gas flows fromevaporators 14 and 15 through an inner passage 18 of a gas heatexchanger 19 and vertical conduit 20 into an absorber comprising avessel 21 and a looped coil 22. In the absorber vessel 21 and coil 22refrigerant vapor is absorbed by a suitable absorbent, such as water,for example, which is introduced into coil 22 through a conduit 23. Thehydrogen or inert gas, Which is practically insoluble and Weak inrefrigerant, is returned to the evaporators 14 and 15 through an outerpassage 24 of the gas heat exchanger 19 and a conduit 25. Thecirculation of gas in the gas circuit just described is due to thedifference in specific weight of the columns of gas rich and weak,respectively, in refrigerant vapor. Since the column of gas rich inrefrigerant vapor and flowing from evaporators 14 and 15 to the absorbercoil 22 is heavier than the gas weak in refrigerant and flowing fromsuch coil to the evaporators 14 and 15, a force is produced or developedwithin the system for causing circulation of ineit gas in the mannerdescribed.

From the vessel 21 enriched absorption liquid flows through a conduit 26and an inner passage 27 of a liquid heat exchanger 28 into the lower endof a vapor lift pump 29 of a generator unit 31). The generator unit 30comprises a heating tube 31 having the vapor lift pump 29 and a boilerpipe 32 in thermal exchange relation therewith, as by welding, forexample. By heating generator unit 30, as by an electrical heatingelement within the lower part of heating tube 31 or by a fluid fuelburner, for example, liquid from the inner passage 27 of the liquid heatexchanger is raised by vapor lift action through pump 29 into the upperpart of the boiler pipe 32. The liberated refrigerant vapor enteringboiler pipe 32 through the pump 29, and also vapor expelled fromsolution in the boiler pipe, flows upwardly into an air cooled condenser33 provided with a plurality of cooling fins 34.

Refrigerant vapor is liquefied in the condenser 33 and returned to theevaporators 14 and 15 through the conduit 17 to complete therefrigerating cycle. Gravity flow of liquid refrigerant is effectedthrough the evaporators, the lower evaporator 14 receiving liquidrefrigerant from the upper evaporator 15. The outlet end of condenser 33is connected by a conduit 35 to the gas circuit, as to the upper part ofthe absorber coil 22, for example, so that any non-condensable gas thatmay pass into the condenser will flow to the gas circuit and not betrapped in the condenser. The weakened absorption liquid, from whichrefrigerant vapor has been expelled, is conducted from boiler pipe 32through a conduit 36, the outer passage 37 of the liquid heat exchanger28 and conduit 23 into the upper part of absorber coil 22.

It will be understood that the evaporators 14 and 15 in Fig. 4 arediagrammatically shown in their relation to. other parts of the system,and that in Figs. 1, 2 and 3 a practical form of the evaporatorstructure in accord with the invention is illustrated in which theevaporator 14 comprises a horizontally disposed coil located essentiallyin a single horizontal plane, and evaporator 15 comprises a verticallydisposed coil projecting upwardly from the horizontal plane ofevaporator 14. The evapa) orator coils 14 and are connected in seriesrelation, and, while all of the conduit connections associated with thecoils may not be immediately evident in Figs. 2 and 3, it is to beunderstood that such connections are generally liketlrose'diagrammatically shown in Fig; 4.

Accordingly, flow of fluids takes place the evaporator coils 14 and 15of Figs. 1, 2- and' 3 in the manner shown in Fig; 4, whereby inert gasfrom conduit enters the horizontal evaporator coil 14 at one end ofaconduit 33 which is positioned parallel to the lateral sides of therefrigerator cabinet and more or less serves as a continuation of thehorizontal portion of conduit 25. From conduit 38 the inert gas passesrearwardly through successive looped portions of the horizontalevaporator coil 14 and then flows upwardly through the verticallydisposed evaporator coil 15. From theupper end of evaporator coil 15inert gas flows to the inner passage 18 of gas heat exchanger 19 througha conduit 39 to which the liquid refrigerant supply line 17 isconnected, the conduit 39 being inclined downwardly toward theevaporator coil 15 or provided with a dam therein (not shown) to causeall of the liquid entering conduit 3? to flow toward the upper end ofevaporator coil 15". Hence, liquid refrigerant passes verticallydownward through evaporator coil 15 and then flows through thehorizontal part of the evap orator structure formed by the coil 14, Withthis arrangement liquid refrigerant flows in the presence of and incounterfiow to inert gas in both the vertical evaporator coil 15 andhorizontal evaporator coil 1 In order to obtain good distribution ofliquid refrigerant in the evaporator coils 1d and 15 and promoteevaporation and diffusion of refrigerant fluid into the inert gas, thecoils may be provided with suitable inserts, such as fine Wire coils orscreens, for example.

Since the inert gas flows successively through the evaporator coils 14and 15, the gas in the horizontal evaporator coil 14 contains a lesseramount of refrigerant vapor than the gas in the vertical evaporator coil15. The partial vapor pressure of the refrigerant is a gradient, so thatthe temperature of liquid refrigerant in the evaporator coils also is agradient, the evaporating temperature of liquid being lower in thehorizontal evaporator coil 14 which constitutes the freezing portion ofthe evaporator structure.

The refrigerating effect produced by the horizontal evaporator coil 14,which is adapted to be operated at temperatures below freezing, isprimarily adapted to effect cooling of the freezing section 11 As shownin Fig. 1, the freezing section 11 comprises a vessel or shell 40 whichextends substantially from one lateral side 41 to the opposite lateralside 42 of the storage space 12. The shell 40 is provided with a frontaccess opening adapted to be closed by a cover plate or closure member43 hinged at 44 in any suitable manner. A shelf or plate-like member 45is provided within shell 40 to the underside of which is heatconductively connected the horizontal evaporator coil 14, the spacebetween the shelf 45 and bottomof the shell 40 holding a body ofsuitable insulation 46, so that evaporator coil 14 will efficientlytransmit cooling effect to matter placed on the shelf, such as trays 47containing water to be frozen, for example. The top 48 of the freezingsection 11 is spaced from the ceiling or roof of the storage space 12 toform a storage chamber 49.

In the preferred embodiment illustrated, the vertical evaporator coil 15is located between the freezing section 11 and the rear insulated wall50 of the refrigerator cabinet. In order to provide a relativelyextensive heat transfer surface, a number of heat transfer members orfins 51 are fixed to the upper and lower horizontally extending arms ofthe coil 15. If desired, a vertical evaporator coil may be employed inwhich the horizontally extending arms are inclined to a marked. degree.In such case a separate bundle of fins or heat transfer members may beindividually fixed to each arm, the arrangement in other respectspermitting the use of tubing which is of smaller size in cross-section,because of the inherent ability of liquid to flow more readily throughthe different parts of the evaporator tubing. The refrigerating effectproduced by the vertical evaporator coil 15, which is adapted to beoperated at a higher temperature than that of evaporator coil 14 anddesirably above freezing, is primarily utilized to cool air in thestorage space 12, the relatively extensive heat transfer surfaceprovided by the fins 51 promoting such air cooling.

As best shown in Fig. 2, the piping 15 and fins 51 form an air-coolingunit which is positioned in a gap between the freezer unit 11 and therear insulated wall 50 of the space 12, the freezer unit 11 in thevertical direction having a major portion of its height coextensive withthat of the air-cooling unit. The opposing vertically extendingimperforate wall sections of the freezer unit 11 and inner liner of thestorage space 12, at the immediate vicinity of the gap, provide avertically extending passage which is always open and completelyunobstructed at the top and bottom ends thereof for flowing air in thespace 12 in thermal exchange relation with the air-cooling unit. It willbe evident that the passage at the rear of the freezer unit 11 extendsvertically for a major portion of the vertical height of the air-coolingunit. I

It will now be understood that the freezing section 11 and highertemperature cooling element, comprising the vertical evaporator coil 15and fins 51 fixed thereto, divide the storage space 12 into the uppercompartment 49 and another lower compartment beneath the freezingsection. in Fig.2 it will be seen that the bottoms of the freezingsection 11 and air-cooling unit at the rear thereof are essentially atthe same level to provide a food storage compartment which extendsdownwardly therefrom at substantially all regions thereof between thelateral side walls 41 and 42 of the storage space 12. 48 of the freezingsection 11 may be constructed as a removable plate or support, andformed either of sheet metal or a synthetic resinous material which isless heat conductive than metal. While in the preferred embodiment thefreezing section 11 extends substantially across the entire width of thestorage space 12, it will be evident that in refrigerators of small sizethe freezing section may extend only part of the distance across thespace;

It has already been pointed out that liquid refrigerant flowssuccessively through evaporator coils 15 and 14, re-

spect'ively. Since the partial pressure of refrigerant vapor in the gasmixture in the vertical evaporator coil 15 is less than the vaporpressure of the warm liquid refrigerant entering conduit 39 throughconduit 17, liquid refrigerant evaporates and diffuses into the gasmixture with consequent absorption of heat from liquid refrigerant inthe evaporator coil 15. Hence, the higher temperature evaporator coil 15not only functions to abstract heat from air in storage space 12 butalso effectively serves as a precooler for liquid refrigerant. frigerantthen flows to the horizontal evaporator coil 14 into the presence ofinert gas which is Weaker in refrigerant vapor, whereby etfective lowtemperature cooling below the freezing temperature is effected in thefreezing section 11.

Since liquid refrigerant entering the horizontal evaporator coil 14 fromthe vertical evaporator coil 15 flows by gravity through the horizontalcoil, it is desirable to arrange successive straight portions and turnsin the direction of liquid How in such a manner that gravity flow of theliquid is promoted from the region 52 to" a lower region at 53. In sucharrangement, it is desirable, of course, to provide a connection 54having aliquid trap 55 for draining excess liquid from the lower end ofthe evaporator structure to the gas circuit, as shown in Fig. 4.

In Fig. 2 the condenser 33 is positioned in an apparatus space'56 atthe-rear of the refrigerator 10. The absorber coil 22 (not shown)desirably is also positioned in the space 56 beneath the condenser, bothof these parts con-- stituting heat rejecting parts which are cooled bynatural The top plate Such precooled liquid redraft circulation of airin the space 56 which serves as a flue for inducing upward circulationof cooling air therethrough. While the COHdflRlII' 33 in Fig. 2comprises four straight sections and connecting bends disposedessentially in the same horizontal plane, such straight pipe sectionsmay be disposed in two or more horizontal planes relatively close to oneanother. In any event, each straight section in the direction of fluidflow is at a slightly lower level than the preceding straight section orslopes downwardly sufficiently to enable liquid condensed therein toflow by gravity toward the outlet end of the condenser and thencethrough the conduit 17 to the upper vertical coil 15 of the evaporatorstructure.

Even though the overall vertical height of the condenser 33 isrelatively small, the arrangement and construction of the evaporatorstructure is such that the evaporator coils l4 and 15 may be locatedclosely adjacent to the roof or ceiling 57 of the thermally insulatedinterior of the refrigerator and still provide a vertically extendingpath of flow of adequate height for liquid refrigerant from condenser 33to the evaporator structure. Stated another way, an adequate liquid headwill be produced in the vertically extending path of flow for liquidrefrigerant condensed in condenser 33, so that gravity flow of liquidrefrigerant through evaporator coils 14 and 15 will be promoted evenwhen the latter are located near the ceiling 57. In such case, ofcourse, no provision is made for an upper compartment 49, as shown inFig. 2. However, under all conditions a small space or gap should beprovided in the cabinet interior adjacent the ceiling 57, so thatnatural draft circulation of air will be effected over the surfaces ofthe evaporator coil 15 and heat transfer members 51 fixed thereto.

The cabinet interior arrangement shown in Figs. 1 and 2, in which thecompartment 49 is provided above the freezer section 11, possessesseveral advantages. One important advantage is that a place is providedfor preserving foodstuffs and liquids, such as butter, lard, shorteningand bottled beverages, for example, at a relatively high temperaturelevel. A temperature range of 11 to 16 C. is particularly suitable forthe compartment 49 and can be attained by providing an apertured top 48for the freezer section 11 and a cooperating movable plate to regulatethe size of the apertures and hence the extent of cooling effecttransmitted to the compartment 49 by the freezer section 11.

Modifications of the embodiment of my invention which I have describedwill occur to those skilled in the art. For example, the top edges ofheat transfer members 51, which are fixed to the U-shaped coil of thehigher temperature evaporator 15, may be substantially at the same levelas the top member 48 of the freezing section 11, so that matter to berefrigerated can be placed on the member 43 and project toward the rearof the storage compartment and occupy the region immediately above thehigher temperature evaporator 15. Therefore, I intend in the claims tocover all those modifications which do not depart from the spirit andscope of the invention.

What is claimed is:

1. A refrigerator including a cabinet having an inner liner defining athermally insulated storage space having a ceiling and an absorptionrefrigeration system associated therewith having a circuit for inert gasincluding piping in said storage space forming low and highertemperature evaporator sections in which refrigerant fluid evaporates inthe presence of the gas, a freezer unit in the storage space comprisingwall means including a horizontal plate to provide a compartmentsubstantially segregated from the remainder of the storage space torestrict circulation of air therebetween, substantially all of thepiping of said low temperature evaporator section being disposedessentially in a single horizontal plane, the piping of said lowtemperature evaporator section being in thermal exchange relation withsaid plate which provides a supporting surface for matter to berefrigerated, an air cooling unit in the storage space comprising meansproviding a relatively extensive heat transfer surface, the piping ofsaid higher temperature evaporator section being in thermal exchangerelation with heat transfer surface and" including a horizontallyextending portion which is nearer to the ceiling of said storage spacethan the piping of said low temperature evaporator section disposed insaid single horizontal plane, means for conducting liquid refrigerant tosaid higher temperature evaporator section for gravity flow therethroughand from the latter to said low temperature evaporator section forgravity flow therethrough, said freezer unit and a vertical wall of saidinner liner having a gap therebetween in which said air-cooling unit isdisposed alongside of said freezer unit with the latter in the verticaldirection having a major portion of its height coextensive with that ofsaid air-cooling unit, and means including opposing vertically extendingimperforate wall sections of said freezer unit and inner liner at theimmediate vicinity of said gap to provide a vertically extending passagewhich is always open and completely unobstructed at the top and bottomends thereof for flowing air in said space in thermal exchange relationwith said air-cooling unit, said passage extending for a major portionof the vertical height of said air-cooling unit.

2. A refrigerator as set forth in claim 1 in which said freezer unit isadjacent to and spaced from the ceiling of the storage space to providea top compartment and the wall means of said freezer unit provides asupporting surface for matter to be refrigerated in such topcompartment.

3. A refrigerator as set forth in claim 1 including a partition in thestorage space to divide the latter into upper and lower compartments,said partition comprising said freezer and air cooling units.

4. A refrigerator as set forth in claim 3 in which said air cooling unitis at the rear of said freezer unit and the heat transfer surfacethereof includes a plurality of vertically extending heat transfer finswhich are in spaced relation and fixed to the piping of said highertemperature evaporator section.

5. A refrigerator including a cabinet having an inner liner defining athermally insulated storage space having a ceiling and lateral sidewalls and an absorption refrigeration system associated therewith havinga circuit for inert gas including piping forming low and highertemperature evaporator sections in which refrigerant fluid evaporates inthe presence of inert gas, conduit means in said circuit including saidpiping for effecting circulation of inert gas solely by the differencein specific weight of columns of inert gas rich and weak, respectively,in refrigerant vapor, a freezer unit in the storage space comprisingwall means to provide a compartment substantially segregated from therest of the storage space to restrict circulation of air therebetween,the piping of said low temperature evaporator section being in thermalexchange relation with said wall means which provides a supportingsurface for matter to be refrigerated, an air cooling unit in thestorage space comprising means providing a relatively extensive heattransfer surface and the piping forming said higher temperatureevaporator section which is in thermal exchange relation therewith,means for conducting liquid refrigerant to said higher temperatureevaporator section for gravity flow therethrough and from the latter tosaid low temperature evaporator section for gravity flow therethrough,said freezer unit and a vertical wall of said liner having a gaptherebetween in which said air-cooling unit is disposed alongside ofsaid freezer unit at the vinicity of the ceiling of the storage space,the bottoms of said freezer and air-cooling units being essentially atthe same level to provide a food storage compartment which extendsdownwardly therefrom at substantially all regions thereof between thelateral side walls of the storage space, and means including opposingvertically extending imperforate wall sections of said freezer unit andinner liner at the immediate vicinity of said gap to provide avertically extending passage which is always open and completelyunobstructed at .the top and bottom ends thereof for flowing air in saidspace in thermal exchange relation with said air-cooling unit, saidpassage extending tor a major portion of the vertical height of .saidair-cooling unit.

Refexenges Cited in the file of this patent UNITED STATES PATENTSBergholm Aug. 13, 194i) Acheson V Sept. 29, 1942 Bixler Nov. 2 1943Beach Mar. 13, 1945 Hedlund May 8, 1945 Ashby Apr. 18, 1950 Miller Dec.5, 1950

